In recent years a substantial amount of work has been devoted to producing bottle caps, and related articles, which are so constructed that they are difficult for children to open. Much of the earlier work can be found in U.S. Patent Office Classification 215-9.
A problem with the earlier work is that, in emphasizing the necessity of making the opening of a container difficult, it concentrated on constructions which are also difficult to manipulate when being used by the infirm, or the elderly. This problem has reached such proportions that it has drawn nationwide attention and is believed to have resulted in urging adoption of optional procedures whereby doctors may specify use of conventional caps for some such patients.